Material for use in preventing offset in printing



Patented Dec. 14, 1937 UNITED STATES MATERIAL FOR USE IN PREVENTING OFF- SET IN PRINTING Reinhard A. Habermaier, Toledo, Ohio, assignor to The De Vilbiss Company, Toledo, Ohio, a

corporation of Ohio No Drawing. Application March 7, 1935, Serial No. 9,832

1 Claim.

This application relates to a method of preventing ofiset in printing and to a composition for use in carrying out the method.

It is old to prevent offsetting of printing by minute particles of solid material spread over the surface of the printed sheet so as to prevent contact of the inked portions of the sheets when piled. These solid particles have been spread on the sheet by spraying a molten material which solidified at ordinary atmospheric temperature and, therefore, became solid particles upon tha sheet.

Broadly speaking, the novel method which constitutes the present invention consists in obtaining a like result in preventing offset by spraying material onto the sheet which dries and leaves a residue of solid particles, instead of leaving the residue by congealing. By changing the sprayed liquid to solid particles by drying instead of by 0 congealing, it is possible to avoid the difficulties incident tomaintaining the material hot until sprayed. Obviously, any means for maintaining material in a molten condition involves providing heat in such a way as to be troublesome and objectionable in connection with a printing press.

It will be apparent that the residual particles which prevent the offset should not be noticeable or materially change the appearance of the paper and for that reason it is preferable that they should be transparent or of a white translucent nature. Also the liquid which is evaporated during drying should be such as does not produce an objectionable odor and should not be harmful from a health standpoint as otherwise exhaust equipment for carrying off the vapor would be necessary. It is also desirable that a material should be such that it can be easily cleaned off when excessive amounts are accidently employed and that it shall be relatively inexpensive.

It will be readily understood that various compositions may be employed which have the necessary or desired characteristics, but'one composition which has been found satisfactory for the purpose is composed of approximately fifteen parts of gum arabic to forty-five parts of water and forty parts of alcohol. The alcohol employed may be the usual denatured ethyl alcohol and gum arabic of standard U. S. P. grade is satisfactory.

The composition may be readily compounded by adding the gum arable to Water in the proportions desired in the final compound; To this mixture is then added the alcohol desired. The alcohol is used to increase the speed of drying of the material, but is not necessary since the aqueous solution may be employed without the addition of alcohol. Of course, other liquids may be employed, if desired, for accelerating the drying speed, the alcohol being cited as a readily available material.

With the composition described a very fine spray can be produced and the resulting particles of dried gum arabic are quite minute. If the particular work being done requires particles of larger size than those obtained from the solution described, gum tragacanth may be added. This increases the viscosity and surface tension of the liquid and consequently increases the size of the drops and dried particles resulting from the spray. One per cent of the total volume' added as gum tragacanth usually increases the size of the particles sufliciently.

Other natural or synthetic gums having the characteristics of gum arabic as to drying and leaving suitable particles for preventing offset may be substituted for gum arabic. Alsodextrin may be employed.

While a somewhat specific composition has been described and some obvious substitutions indicated, it will be understood that these are by way of example rather than by way of limitation, and that in its broader aspect the invention applies to the use of a liquid which can be readily sprayed and which contains material which will readily dry to leave on the surface of the paper a solid residue of particles sufiiciently firm to space the paper and prevent offset and at the same time being transparent or white translucent in color. The fundamental feature of the method is that the solid particles are obtained upon the printed paper by means of drying a spray rather than by freezing sprayed liquid, and the size of the drops 'is regulated by suitable ingredients.

What I claim is:

A composition of matter for preventing offset in printing consisting of substantially fifteen parts of gum arabic, forty-five parts Water, forty parts denatured alcohol and one part gum tragacanth.

REINHARD A. HABERMAIER. 

